Centrifuge for continuously separating semisolid constituents



- Apnl 25, 1939. E. A. FORSBERG CENTRIFUGE FOR CONTINUOUSLY SEPARATING SEMISQLID CONSTITUENTS Filed Aug 27, 1934 m ll h lH mm 11 s o I 3 s i 7/4"? 15 this kind of work.

Patented Apr. 1939 UNITED, STATES commoner-i sarmoss-rs csnrmiuos ma ans-ruse ssmsoun cons Erik A l We Separator Stockholm, SM, n-

"r to The De Ian! company, New York, N; Y., a corporation of New Jersey Application sum :1. 19:4, Serial No. 141,058 In Sweden September 2, 1983 In centrifugal separators in which two liquids are separated the one from the other (e. g., common milk separators) it is generally not diiiicult continuously to discharge the separated products,-

as the nature of liquids makes them easily ,movable within and out of the heavy and light liquid zones formed in the separating chamber. The conditions, however, are diiierent it one of the separated products, and particularly the heavier one, consists of or largely comprises solids These cannot leave the bowl automatically. but special arrangements pelling them. Anumber of constructions, socalled sludge separators,

There is. however, also, a third condition to which neither the common separators nor the sludge separators are adaptable and that is when one separated product is of a semi-solid doughy 20 nature. In case it is heavier than the liquid it has been possible in some instances, as for example in the so called yeast separators, to secure acceptable results by providing the bowl with narrow outlets at or in the neighborhood of the periphery and by giving the bowl wall-such a shape that'the separated matters slide toward such outlets. However, bowls of this type work) in a satisfactory manner with only certain "materials and do not allow 'thedischarge of the. product in a more or less high- 3o heavier separated ly concentrated form, which is often desirable. And they are of course quite useless if the semisolid product is-lighter than the liquid.

The last named condition sometimes exists.

5 As a typical example may be mentioned the separation of paramn from mineral oil (crude oil,- distillate or. distillation residues) after it has been diluted with a heavy liquid itrichlorethylene or the like) and chilled to a low temper 40 ature. The paraiiin is removed as the lighter constituent and accumulates in the central part oi the bowl, whence it outflows to and through the outlet for the lighter constituent. Such a process is described in the Backlund Patent No.

5 1,676,069. In carrying out this process it has been customary to supply the mixture in the usual manner through a central feed tubeto the separating chamber and distribute theunixture aligning holes in a therein through vertically 0 pile of conical discs. The separated heavy solution of oil and solvent flows from theperipheral portion of the bowl upwardly into a chamber neck and thence out over a weir plate in the bowl which is exchangeable or adjustable forreguss lation of the leveL. The separated lights;- doughy are required for exhave been devised for (01. ass-es) or viscous paraiiin fllls a chamber between the control feed tube andthe inner edges pi the discs and thence flows upwardly over a collar projecting inward from the bowl top and through holes in the bowl top or neck above the collar.

A bowl of this type works in a satisfactory manner as long as the paraii'ln is of not too high a viscosity and the quantity is not too large. Under these conditions the radial differences of level which are necessary for forcing the paraiiin 1o axially to the edge ofthe collar are not greater than ispermissible from the point of view of practicaland convenient dimensions of'the bowl.

- However, if the paraflln has great inner friction (that is,.if it be coarse crystalline and especially needle crystalline),- .large radial diilerences' of level are of course required in order to produce the axial flow which is necessary for the dis-- charge of the paraflln. The condition will of course be similar if the quantity of paraflin be large and therefore necessitate a great axial rate of flow. In these circumstances it is necessary either to facilitate the axial'movement of the mass by special mechanical scraper devices, or to shorten the axial path through which the mass must move in order to leave the bowl. Constructions designed to accomplish the first of these results are known (see Forsberg Patent No. 1,699,286) and sometimes operate emciently, although they introduce an undesirable complication. In order to shorten the axial path of flow the bowl has been provided with paraiiin outletsin both ends, but with this expedient also the capacity of the bowl is limited, not by its separating ability, but byits ability to discharge the paraflln, unless the bowl is made impracticably low in relation to its diameter. .With present arrangements it isthus not possible fully toutilize the real separating capacity of the bowl when the quantity of peraflin is large or when the paraiiin is heavy, without using expensive and complicated mechanical constructions.

- The present invention comprises an arrange- .ment-that makes it possible to takeout the separated lighter constituent in other places than wat the ends of the chamber in which-the, said constituent accumulates inthe bowl. lhe invention thus makes'it possible to take" out the separated mass in several diiferent places at -a, small axialdistance one from the other. The separated therefore has tognoye a desired short distance in axial direction, and,

portion ofthe whole quantityneed be taken out. Thereby, even with an heavy sepas5 at each place of discharge "only a desired small rated product, or in-case the relative quantity of such product should be considerable, the radial differences of level which are possible in practice become sufficient for producing the axial movements that are necessary in order to remove such product.

In the drawing:

Fig. 1 is a vertical sectional view of a centrifugal separator embodying the invention.

Fig. 2 is a partial vertical section of a modification.

Fig. 3 is a detail perspective view of .one of the scrapers, shown in Fig. 1, for deflecting the lighter separated material in such manner as to facilitate its discharge from the separator bowl.

The mixture to be separated is supplied through the central tube I and passes through the channels 2 and the holes 3 to the discs 4, between which the separation takes place. The heavy liquid discharges through channels 5, which may be provided with devices I for regulating the discharge level, which devices are shown in Fig. 1 as regulating screws but may be of other constructions, as, for example, exchangeable rings, as shown at la in Fig. 2 The lighter constituent collects in the chamber 8, whence it is to be removed from the bowl. If this latter constituent were free flowing, as, for instance, the

cream in a common milk separator, it could di-' rectly discharge through the outlet ID. A certain difference of pressure is of course necessary in order that a discharge shall take place, but if thematerial has a low viscosity, a very small radial difference of level is suiiicient for the discharge of evencomparatively large quantities.

If, on the other hand, ,the material has a high viscosity, its inner surface must assume a slanting position, so that almost the whole chamber. to the central tube l becomes filled and the bowl becomes clogged.

In order to facilitate the discharge from the bowl of the separated product in question and thus avoid the inconveniences referred toabove, one or, preferably, several scrapers I I, I2 are provided in the chamber between the inner rims of the discs I and the central tube I, the said scrapers working into the rapidly rotating surface of ,the lighter separated product and throwing it in axial or nearly axial direction towards the open end of the bowl, which, in the type of machine shown, is its upper end. Theshape of the scrap- I ers may be varied. A suitable arrangement is to construct the scrapers as spiral-formed chutes, as indicated at H. Another shape is shown in Fig. 2, where the scraper simply consists of a bent wing l2. The scrapers are suitably flxed to a stationary'holder, which may be in the form.

of a tube IS. The scrapers are placed at different heights and on different radii, so that a will be removed in each place and the higher scraper does not hinder the material from being thrown out from a lower one. It is of course also possible to arrange two or more scrap ers at the same height in order to obtain a more symmetric load. The inner surface of the separated mass assumes a wave-like aspect, as indicated at G in the figures. The axial distance 1 between the scrapers proper and between the outermost scraper and the outlet I0 is selected with regard to the amount and nature of the material which is to be: brought away. The greater the number of scrapers in axial direction, the smaller the amount of the mass which greater the sloping which can be permitted for each wave of the inner surface; both of which condito the side. The deflector may be in flxed rela- 5 tion to the holder 13 or to the collecting vessel 9, as shown in Fig.2, or it may be fixed to the bowl, as in Fig. l. The former construction is the simpler, but the latter has the advantage that the deflector is kept free from the mass 10 by the centrifugal force.

The holder l3 may be a fixed one or it may to a certain degree participate in the rotation of the bowl. The latter arrangement is better adapted to keeping the deflector l4 clean and 15 (principally) to reducing the wear of the scrapers IL or I2 and the stresses on the parts. If the mass is of a-coarse grinding nature, the wear and the stresses on the scrapers would become too great if their relative speed were kept at a 20 value which corresponds to the usual speed of separator bowls. The holder and the scrapers fixed thereto should therefore be caused to rotate in the same direction as the bowl, but at a reduced speed. The desired movement is suitably generated by allowing the holder to be rotatedby contact with the separated mass but braking it with a certain force; the speedof course being regulated by the force of braking applied. Any

type of braking may be used: mechanic, hydraulie, electric or magnetic. In Fig. 2, I5 represents a mechanical braking member consisting of a brake-band carried by an arm l6 secured to the 'machine frame.- The tubular holder iii, to which the scrapers l2 of Fig. 2 are secured, is carried by the upper collecting vessel 9. If this vessel .were laid loosely upon the lower collecting vessel (which is secured to the. main frame), it

would, unless restrained, freely rotate, due 'to the rotary action of the separated paraiiin upon the 40 scrapers l2. However, the brake-band l5 restrains vessel 9, holder l3 and scrapers I! from free rotation, The tension of the brake-band is adjusted to allow the members 9, l3 and I! to rotate, but at a reduced speed, so as to allow the scrapers to function as described and at the same time avoid imposing upon them any dangerous stress or strain. The machine works in the following manner.

After the bowl has been started and the liquid has been admitted, separated lighter product beginsto collect in the chamber 8 which by and by becomes filled towards the center. After some time the mass reaches the scrapers and begins to be thrown out in axial direction. Be- 66 tween the scrapers, however, the mass continues moving inwards to the center, ridges or swells as those shown at '6 in Fig. 1 thereby being formed. Under the influence of the centrifugal force the mass begins to float axially from the ridges towards the valleys, which are kept free from the mass by the scrapers. An equilibrium is reached when the movement of the mass towards the valleys takes-place at the same rate as the separating procedure. By suitably choosing the form, size and number of the scrapers; and if necessary also their rotation speed, the scraper device can beregulated to cope with separated material of different amounts and nature.

What I claim and desire to protect by Letters v Patent is:

a 1. A centrifugal separator adapted for the separation'of constituents of which the lighter is comparatively not free-flowing, comprising a rotatable bowl provided with an outlet for the 16.-

brake the holder so as to compeLthe scraper or v scrapers to rotate at a speed below the rotation speed of the separated mass.

2.-In a centrifugal separator adapted for th separation of constituent materials of which the lighter is comparatively viscous and provided with an outlet for such lighter viscous material, means for facilitatingtheremoval of said lighter viscous material from an annulus thereof surrounding the center of the bowl comprising a relatively stationary open trough scraper located at the central part of the bowl and of short length relative to the radius of the bowl and whose outer end is distant from the periphery of the bowl, said scraper having a surface starting from its outer end at approximately the-inner surface of the annulus as a spiral of decreasingradius and gradually changing in an upward direction to approximately a radial plane with its discharge end substantial go inside the exit from the bowl.

3-. In a' centrifugal separator adapted for the separation of constituent materials of which the lighter is comparatively viscous aiid provided with an outlet for such lighter viscous material,

viscous material from an annulus thereof surrounding the center of a centrifugal bowl comprising a relatively stationary scraper consisting of a shallow, open trough concavely curved in cross section-and located entirely in-the central zone of the bowl and adapted, as the annulus moves toward the center of the bowl,,to

contact it and remove material therefrom, said' scraperhaving a center line starting, from its outer .end, at its locus of contact with the inside of the annulus, as a. spiral of decreasing radius approximately in a plane at right angles with the center line of the bowl and gradually changing in a smooth curve'to a line approximately mately in a plane at right angles towthefaxls means for facilitating the removal of said lighter 9 parallel with the centerline ofthe bowl, said.- trough ending substantially nearer in an axial direction to its pointpf beginning than the exit,

of the bowl and gradually changing in a smooth center line of the bowl, said scrapers being spaced apart in an axial direction. 1

5. In a centrifugal separator adapted for the separation of constituent materials of which the lighter is comparatively viscous and provided with an outlet for such lighter viscous material.

' means for facilitating the removal of said lighter viscous material from an annulus thereof surrounding the center of the bowl comprising relativelystationary open trough scrapers positioned wholly within the central zone of the bowl and curve .to a line approximately parallel with the from their outer ends extending inward' and upward from said annuluseachof which has a center line starting from its outer end as a spiral of decreasing radius approximately in a plane at right angles to the axis of the bowl and gradually changing in a smooth curve to a line approximately parallelwith the center line of the bowl, different scrapers being positioned on different radii of the bowl and at diflerent distances from said outlet so as to form substantially noninterfering columns of the lighter viscous outflowing material.

-- c. In a centrifugal separatoradapted for the lighter is comparatively ;viscous and provided with an outlet for such lighter viscous material. -means for facilitating the removal of said lighter viscous' material from .an annulus thereof surrounding the center of the bowl comprising a relatively stationary open trough scraper located wholly in the central part of the bowl and extending inwardandupward from said annulusand 'havinga. center line starting as a spiral of separation of constituent materials of which the 4 decreasing radius approximately in a plane at right angles to the axis ofthe bowl and'gradu proximately parallel with the center line of the bowl andadapted to pare .off a thin strip from the-interior of the rapidly moving annulus and, while the material is stfll moving due to its inertia, guide it in an axial direction first toward the center of the bowl and then in an axial means for facilitating the removal of said lighter viscous material from an annulus thereof surrounding the center of the bowl comprising a ally; changing in a smooth curve to a plane aprelatively stationary open trough scraper located wholly in the central partof the bowl and having a warped-surface starting at the inner surface of the annulus 'as a spiral of d radius andgradually changing in an upward direction to approximately a.radial plahe and adapted to pare oil a thin strip from the interior of the rapidly moving annulus and, while the material is still moving due to its inertia, guide it in an axial directionflrst toward the center of the bowl and then in an axlal direction toward the exit of the bowl.

ERIK AUGUST I'ORSBIRG. 

